1. Field of the Invention
This invention relates to color switchable sensors, and more particularly, to a color switchable sensor containing both fracto-mechanoluminescent and elasto-mechanoluminescent materials for both visually and remotely detecting the transition point between stress and fracture in a structure, e.g., aircraft and/or ship components possibly due to hydrodynamic drag, by an optic waveguide.
2. Description of the Prior Art
Glassy, plastic, polymer and composite among many different structural materials during both manufacture and use require integrity and robustness monitoring in situ and in real time in order to ascertain damage leading to failure of the structure. Usually, the failure is the result of a progression from initial stress to the structure to an eventual fracture. Monitoring the stress on a structure would allow for repair of the structure prior to fracture. Sage et al. in U.S. Pat. No. 5,905,260 recites to a damage sensor using triboluminescent materials connected to light guiding fibres or layers embedded within the structure or mounted on the structure's surface to detect the physical damage to the structure. The triboluminescent materials disclosed in Sage et al. are all fracto-mechanoluminescent materials emitting different wavelengths of light when fractured. The wavelength of emission can be used, through an algorithm, to directly locate the position of the fracture.
There is a need to know prior to the occurrence of a fracture where and when a fracture could occur to a structure in order that a fracture can be prevented with repair.